Born in Kent in 1869, Carl Mermagen was aged around thirty and a teacher at Credition Grammar School when he became a leading local footballer on moving to the area in the late 1890s. As well as turning out for Exeter United, he organised a "Mr C .F. Mermagen's XI" to face the likes of St Sidwell's United in the early 1900s.

From a family of teachers, his brother Lothar was instrumental in the resurrection of Colyton Grammar School in 1905 (after a five year closure) and Carl himself actively promoted association football in Credition with the school's team also featuring in regular friendlies against teams from Exeter. Many years later in 1920 his son Carl appeared for the Exeter Midweek League against City's reserves whilst nephew Patrick (also a teacher), son of brother Lothar, played a number of first-class games for Somerset in 1930.

Soon after his participation in football in Exeter, Mr Mermagen - who was educated at Sherborne School and Trinity College Dublin - was ordained into the Church of England. Having likely to have been initially posted to the Falkland Islands, he was attached to a parish in Tamworth by 1910. Remaining in Staffordshire, he died in 1934 at the age of sixty-four.